The export of chemically bound nitrogen from land to sea and the impact of such export on the ecosystems of the continental shelves have caused considerable concern.
A goal of a 50% reduction of the nitrogen export to the North Sea and the Baltic Sea has been adopted by the Oslo-Paris and Helsinki Commissions, and action programmes have been initiated to reduce the emissions of nitrogen to both water and air. However, trend analyses and source apportionments of nitrogen loads carried by major Western and Eastern European rivers have demonstrated that the cited reduction goals can not be reached, unless the loss of nitrogen from agricultural land to water is substantially reduced.
The general objective of the proposed project is to develop improved procedures for regional analysis of tne export of nitrogen from land to sea and to investigate the controllability of this export. To achieve this objective, we will focus on subsurface retention of nitrogen and integrate and validate existing models of diffuse emissions to water and subsurface retention on a regional scale.
The following specific research objectives have been identified:
- to combine a general hydrogeological residence time model with a more detailed model of nitrogen fluxes in arable soils to form a regional model of the input of nitrogen to the saturated zone;
- to combine residence time estimates for the saturated zone with information regarding denitrification conditions to obtain estimates of the retention of nitrogen in the saturated zone on a regional scale;
- to derive empirical models of nitrogen deliveries to freshwater in intensively monitored river basins for which land use data are available either on subbasin or field level;
- to validate the proposed models in catchments subjected to different agricultural practices and representing different geological and climate conditions;
- to incorporate empirical and theoretical models of subsurface retention of nitroge into a GIS-system for regional analysis of the im pact that changes in agricultural practices may have on the future export of nitrogen from land to sea.
Funding SchemeCSC - Cost-sharing contracts